This invention relates to a panel processing apparatus for use in the process of manufacture of color television picture tubes including means for automatically fitting a shadow mask in a panel and means for detecting the condition in which the shadow mask is fitted in the panel.
In the process for manufacture of color television picture tubes, a coating of black matrix, coatings of phosphors and a coating of an emulsion are applied to the inner surface of each panel by following a plurality of coating steps, after a coating of a photo-resist is formed on the inner surface of the panel by applying the photo-resist thereto and then exposing the photo-resist layer to a light source through a shadow mask. In applying these coatings by following the plurality of coating steps, predetermined operations are successively performed in sequence without interruption and mounting and detaching of the shadow mask in and from the panel are frequently effected repeatedly when the operation shifts from one step to another. In order to automatically perform these coating operations, it is necessary to continuously convey the workpieces in the production line. When a series of operations are continuously performed, almost all the panels in the production line will become unacceptable for specifications if trouble arises and the movement of the workpieces is stopped. Therefore, it is essential, from the point of view of increasing efficiency in production, that either the movement of the workpieces not be stopped or the normal condition be restored to the production line as soon as possible once the movement of the workpieces in the production line is stopped.
One problem encountered in such apparatus and causing trouble is that a shadow mask may not be fitted completely in a panel in the step of fitting the shadow mask in the panel due, for example, to variations in the sizes of the shadow mask and the panel. For example, the shadow mask may be fitted in the panel in what is referred to as two-pin mounting in which only two of more than three pins of the panels engage the shadow mask or in what is referred to as one-pin mounting in which only one pin of the panel engages the shadow mask. In such a case, the shadow mask tilts and projects from the panel sealing surface because the rest of the pins do not engage the shadow mask.
This problem results in the shadow mask interfering with the operation of shadow mask mounting means or panel conveyor means, thereby stopping the movement of the workpieces or causing damage to the apparatus.